The present invention relates to a process for the preparation of compounds containing primary aromatic amino groups, urethane groups and polyester groups by alkaline hydrolysis of suitable isocyanate prepolymers and the products of this process.
Compounds containing primary aromatic amino groups and ester groups are known. German Auslegeschrift No. 2,447,748 is directed to a process for the preparation of polymeric polyamines from a polyurethane prepolymer. The prepolymer may be prepared from a polyester polyol and excess diisocyanate. The polyamine is produced by complex formation of the prepolymer with a virtually anhydrous, non-oxidizing organic or inorganic acid. The complex is then destroyed and the mixture is neutralized with an aqueous alkaline solution. Urethane oxypropylene aminodiamino-oligoesters are taught to be useful as hardeners for macrodiisocyanates in Russian Patent No. 538,003.
In U.S. Pat. No. 3,385,829, it is disclosed that nitroarylpolyurethanes which can be converted into the corresponding amines by catalytic hydrogenation may be prepared by reacting polyhydroxyl compounds, (e.g. polyhydroxyl compounds based on polyesters) with nitroarylisocyanates. It is also taught in that disclosure that products which are formed by the reaction of aromatic diisocyanates with polyol compounds (e.g. polyesters) can be converted into compounds containing formyl amido groups by means of formic acid. The formyl amido groups may then be hydrolyzed with dilute acids or bases to form amino groups.
In German Offenlegungsschrift No. 1,056,367, polypropylene glycol ethers are esterified on one side with aliphatic or aromatic dicarboxylic acids and the remaining carboxyl groups are reacted with excess diamines at 130.degree. to 230.degree. C. so that only one NH.sub.2 function is bound as an acid amide.
German Auslegeschrift No. 2,546,536, discloses a process in which hydroxyl group-containing ketimines, aldimines or enamines are reacted with compounds containing isocyanate end groups. Hydrolysis of the resulting polyketimines, polyaldimines or polyenamines yields compounds containing amino end groups. If the hydroxyl group-containing enamines are alkylated on the nitrogen, polyesters may also be used to prepare the compounds containing isocyanate end groups and compounds containing ester groups and secondary aliphatic amino groups are obtained.
Each of these processes is either expensive and complicated and/or yields products which are too highly viscous for most applications. The reactions involved in the known processes also take place under conditions in which a considerable proportion of the original ester groups are destroyed, e.g. with simultaneous hydrolysis, amide formation or transesterification. Consequently, these processes are not commercially significant.